1. Field of the Invention
The present invention relates to a color image processing apparatus for processing a color image signal in a color copying machine or the like.
2. Description of the Prior Art
Conventional color original reading using a line sensor such as a CCD has been proposed. As shown in FIG. 1, color separation filters (e.g., red R, green G and blue B) are sequentially formed by vacuum deposition or the like on the corresponding light-receiving elements of a one-dimensional sensor. An original image is color-separated by the one-dimensional sensor to read the original image. This conventional system is receiving a great deal of attention due to the following advantages and will be used in a variety of applications:
(1) A special tricolor separation optical system is not required and the apparatus as a whole can be made compact. PA1 (2) The optical system or the like can be easily adjusted and color misregistration is prevented.
However, since such a one-dimension sensor generates serial tricolor image data, a high-speed driver is required to read the original image with a high resolution. In addition, in order to obtain accurate image data, a required peripheral circuit arrangment results in high cost and a large size.
FIG. 2 is a timing chart showing an output signal from the one-dimensional sensor. The signals charged by the R, G and B filters of the line sensor shown in FIG. 1 in accordance with the light intensities of the incident light components are voltage-converted to color signal pulses R.sub.N, G.sub.N, B.sub.N, R.sub.N+1, G.sub.N+1, B.sub.N+1, R.sub.N+2, . . . which are serially generated. Assume that a set of pulses R.sub.N, G.sub.N and B.sub.N of FIG. 2 constitutes a color image signal for one pixel, and that a time T.sub.1 is required to generate this color image signal. At time T.sub.2 for generating one color signal pulse R.sub.N, G.sub.N or B.sub.N is illustrated in FIG. 2 as follows: EQU T.sub.2 =T.sub.1 /3
In a high-speed, high-resolution apparatus, the read time is extremely short. For this reason, an external amplifier circuit for receiving the high-speed pulses must have good high-frequency characteristics, so that the circuit arrangement is complicated and costly. However, when a simple circuit arrangement is used in place of a complex high-speed amplifier circuit, only a distorted output, as shown in FIG. 3, is obtained.
Even if an external circuit having good high-frequency characteristics is used, the pulses from the sensor are subject to disturbance along the signal lines up to the external amplifier circuit. As a result, only the distorted waveform shown in FIG. 3 is obtained.
Serial high-speed pulses suitable for electrically performing masking and undercolor removal so as to produce optimal image signals cannot be realized by using the tricolor signal obtained as described above.